1. Field of the Invention
The present invention relates to a traffic information distribution method and a traffic information distribution apparatus for distributing traffic information regarding a traffic situation to a car navigation system and an in-vehicle terminal for receiving the distributed traffic information and displaying the distributed traffic information on a display apparatus.
2. Description of the Related Art
Conventionally, there is VICS (Vehicle Information and Communication System) (registered trademark) managed by Vehicle Information and Communication System Center (hereinafter referred to as VICS (registered trademark) Center) in Japan as a system for distributing traffic information regarding a traffic situation to a vehicle. In VICS (registered trademark), the traffic information such as traffic jam information on a road and travel-time of a route is calculated based on real-time traffic information collected by on-road sensors (e.g. an ultrasonic sensor, a loop coil sensor, an optical beacon, and an imaging device and the like) managed by prefectural police and a road administrator, and the calculated traffic information is distributed to an in-vehicle terminal equipped with a vehicle via a narrow band communication means such as an optical or radio beacon or a wide band communication means such as FM multiple broadcasting.
In recent years, because it becomes common to equip a vehicle with a car navigation system, a VICS (registered trademark) terminal is rarely used alone and the car navigation system often doubles as the VICS terminal. To the car navigation system, not only the traffic information provided by VICS (registered trademark) but also the traffic information of which added value is increased by processing the traffic information provided by VICS (registered trademark) (e.g. predicted traffic information and the like) are distributed via the Internet and a communication network of mobile phones in response to a request from each driver.
In VICS (registered trademark), a link which can provide the traffic information is limited to a link where an on-road sensor is installed, and thus limited to a predetermined link (the link is referred to as “a VICS (registered trademark) link” hereinafter). The number of the VICS (registered trademark) links has been increasing year by year due to road improvement and installation of on-road sensors, and it also becomes possible to collect and provide traffic information obtained from a link different from the VICS (registered trademark) link due to development of the probe technology of a traffic situation. Thus, it is expected that the amount of the traffic information distributed to the car navigation system from a traffic information distribution center will keep increasing. Therefore, it is desired to reduce the amount of the traffic information distributed to the car navigation system from the traffic information distribution center.
Japanese Laid-open Patent Application No. 2006-84257 discloses a technique which employs difference distribution to reduce the amount of the traffic information which is distributed to the car navigation system from the traffic information distribution center. When the traffic information is distributed in the difference distribution, only a part of the traffic information different from the traffic information distributed before (difference information) is distributed. With this difference distribution, because only the difference information is distributed, it is possible to reduce the amount of the traffic information distributed compared to a case where entire information of the traffic information is always distributed.
When the difference information is distributed many times and a car navigation system to receive the difference information at some point in time, generally the terminal can neither reproduce information based on the difference information which has been failed to be received nor reproduce information based on the subsequent difference information even if the terminal succeeds to receive the subsequent difference information. To allow the terminal to reproduce the traffic information correctly in the above case, the traffic information distribution center needs to store and manage a version or date-time information of the traffic information the car navigation system holds.
When the difference information is distributed form the traffic information distribution center to the car navigation system, because a communication between the traffic information distribution center and the car navigation system is carried out via radio waves, it is likely for the car navigation system to fail to receive the distributed traffic information when a vehicle is in a place where reception of the radio waves is not good, such as in a tunnel.
Conventional techniques including the technique disclosed in the Japanese Laid-open Patent Application No. 2006-84257, however, manages neither a version of information which is a basis of difference information nor a version of the traffic information held by the car navigation system. With the conventional techniques, it is expected that when distribution of the traffic information from the traffic information center to the car navigation system fails, the car navigation system cannot reproduce the traffic information in a high ratio.
In view of the above problems, an object of the present invention is to provide a traffic information distribution method, a traffic information distribution apparatus and an in-vehicle terminal which can reduce the amount of the information distributed and improve reliability of information distribution in distribution of the traffic information to the in-vehicle terminal such as the car navigation system.
A first aspect of the preset invention provides a traffic information distribution method implemented in a computer which acquires or generates traffic information on a road traffic situation and distributes the traffic information individually to each of in-vehicle terminals equipped with vehicles, the method allowing the computer to perform the steps including: a traffic information accumulation step of, at the time when the computer acquires or generates the traffic information, including predetermined identification information in the traffic information and accumulating in a storage device the traffic information which includes the predetermined identification information; a distribution request information reception step of receiving distribution request information transmitted from the in-vehicle terminal and containing identification information which is included in reference traffic information the in-vehicle terminal holds at the time when the in-vehicle terminal transmits the distribution request information; a difference traffic information generation step of generating difference traffic information between the traffic information stored in the storage device and having a same identification information as the identification information included in the reference traffic information contained in the received distribution request information and the traffic information which is to be distributed at the time when the difference traffic information is generated; and a traffic information distribution step of distributing the generated difference traffic information to the in-vehicle terminal.
A second aspect of the present invention provides a traffic information distribution method implemented in a computer which distributes predicted traffic information regarding a road traffic situation individually to each of in-vehicle terminals equipped with vehicles, the computer including a predicted traffic information accumulation unit for accumulating at least a group of a plurality of pieces of the predicted traffic information, each piece of which pertains to a different time that belongs to a same time-line, the method allowing the computer to perform the steps including: a distribution request information reception step of receiving from the in-vehicle terminal distribution request information which requests the computer to distribute the predicted traffic information; a reference information selection step of selecting one of the plurality of pieces of the predicted traffic information, each piece of which pertains to a different time that belongs to the same time-line, as a reference traffic information, when the received distribution request information contains a distribution request of the plurality of pieces of the predicted traffic information, each piece of which pertains to a different time that belongs to a same time-line; a difference traffic information generation step of generating difference traffic information between the predicted traffic information which is not selected as the reference traffic information and the reference traffic information; a traffic information distribution step of distributing entire information of the predicted traffic information selected as the reference traffic information and the difference traffic information between the reference traffic information and the predicted traffic information not selected as the reference traffic information to the in-vehicle terminal.
A third aspect of the present invention provides a traffic information distribution method implemented in a computer which distributes real-time traffic information on a road traffic situation at once to in-vehicle terminals equipped with vehicles, the method allowing the computer to perform the steps including: a real-time traffic information acquiring step of acquiring the real-time traffic information at a predetermined interval; a reference traffic information selection step of selecting the real-time traffic information acquired at the predetermined interval at the real-time traffic information acquiring step as a reference traffic information once in a predetermined times the real-time traffic information is acquired; a difference information generation step of generating difference traffic information between the real-time traffic information which is not selected as the reference traffic information among the real-time traffic information which has been acquired at the real-time traffic information acquiring step and latest reference traffic information; a traffic information distribution step of distributing entire information of the real-time traffic information selected as the reference traffic information and the difference traffic information between the reference traffic information and the real-time traffic information which is not selected as the reference traffic information to the in-vehicle terminals.
A fourth aspect of the present invention provides a traffic information distribution method implemented in a computer which distributes predicted traffic information regarding a road traffic situation at once to in-vehicle terminals equipped with vehicles, the computer including a predicted traffic information accumulation unit for accumulating at least a group of a plurality of pieces of the predicted traffic information, each piece of which pertains to a different time that belongs to a same time-line, the method allowing the computer to perform the steps including: a reference traffic information selection step of selecting a piece of the plurality of pieces of the predicted traffic information having the different times as reference traffic information; a difference traffic information generation step of generating difference traffic between the predicted traffic information which is not selected as the reference traffic information and the reference traffic information; a traffic information distribution step of distributing entire information of the predicted traffic information which is selected as the reference traffic information and the difference traffic information of the predicted traffic information which is not selected as the reference traffic information to the in-vehicle terminals.
A fifth aspect of the present invention provides a traffic information distribution apparatus which acquires or generates traffic information on a road traffic situation and distributes the traffic information individually to each of in-vehicle terminals equipped with vehicles, the apparatus including: a traffic information accumulation unit for including a predetermined identification information in the traffic information and accumulating in a storage device the traffic information which includes the identification information when the traffic information distribution apparatus acquires or generates the traffic information; a distribution request information reception unit for receiving distribution request information transmitted from the in-vehicle terminal and contains identification information included in reference traffic information the in-vehicle terminal holds at the time when the in-vehicle terminal transmits the distribution request information; a difference traffic information generation unit for generating difference traffic information between the traffic information stored in the storage device and including a same identification information as the identification information included in the reference traffic information contained in the received distribution request information and the traffic information which is to be distributed at the time when the difference traffic information is generated; and a traffic information distribution unit for distributing the generated difference traffic information to the in-vehicle terminal.
A sixth aspect of the present invention provides a traffic information distribution apparatus which distributes predicted traffic information regarding a road traffic situation individually to each of in-vehicle terminals equipped with vehicles, including: a predicted traffic information accumulation unit for accumulating at least a group of a plurality of pieces of the predicted traffic information each of which pertains to a different time that belongs to a same time-line; a distribution request information reception unit for receiving from the in-vehicle terminal distribution request information which requests the traffic information distribution apparatus to distribute the predicted traffic information; a reference traffic information selection unit for selecting as reference traffic information one of the plurality of pieces of the predicted traffic information each of which pertains to a different time that belongs to the same time-line when the received distribution request information contains a distribution request of the plurality of pieces of the predicted traffic information each of which pertains to a different time that belongs to the same time-line; a difference traffic information generation unit for generating difference traffic information between the reference traffic information and the predicted traffic information which is not selected as the reference traffic information; a traffic information distribution unit for distributing entire information of the predicted traffic information selected as the reference traffic information and the difference traffic information of the predicted traffic information which is not selected as the reference traffic information.
A seventh aspect of the present invention provides a traffic information distribution apparatus which distributes real-time traffic information on a road traffic situation at once to in-vehicle terminals equipped with vehicles, including: a real-time traffic information acquiring unit for acquiring the real-time traffic information at a predetermined interval; a reference traffic information selection unit for selecting as reference traffic information a piece of the real-time traffic information acquired by the real-time traffic information acquiring unit at the predetermined interval once in a predetermined times the real-time traffic information is acquired; a difference traffic information generation unit for generating difference traffic information between latest reference traffic information and the real-time traffic information which is not selected as the reference traffic information among the acquired real-time traffic information; a traffic information distribution unit for distributing entire information of the real-time traffic information selected as the reference traffic information to the in-vehicle terminals, and distributing the difference traffic information of the real-time traffic information which is not selected as the reference traffic information to the in-vehicle terminals.
An eighth aspect of the present invention provides a traffic information distribution apparatus which distributes predicted traffic information regarding a road traffic situation at once to in-vehicle terminals equipped with vehicles, including: a predicted traffic information accumulation unit for accumulating at least a group of a plurality of pieces of the predicted traffic information each of which pertains to a different time that belongs to a same time-line, a reference traffic information selection unit for selecting one piece of the plurality of pieces of the predicted traffic information each of which pertains to a different time that belongs to a same time-line; a difference traffic information generation unit for generating difference traffic information between the predicted traffic information which is not selected as the reference traffic information and the reference traffic information; a traffic information distribution unit for distributing entire information of the predicted traffic information selected as the reference traffic information to the in-vehicle terminals and the difference traffic information of the predicted traffic information which is not selected as the reference traffic information to the in-vehicle terminals.
A ninth aspect of the present invention provides an in-vehicle terminal which is linked to a traffic information distribution apparatus for distributing traffic information, including: a reference traffic information reception unit for receiving as reference traffic information entire information of the traffic information that the traffic information distribution apparatus acquires or generates and includes a predetermined identification information; a traffic information storage unit for storing the received reference traffic information; a distribution request information transmission unit for configuring a distribution request which requests the traffic information distribution apparatus to distribute latest traffic information to include an identification information of the reference traffic information stored in the traffic information storage unit, and transmitting the distribution request information; a difference traffic information reception unit for receiving difference traffic information distributed from the traffic information distribution apparatus in response to the transmitted distribution request information; a traffic information reproduction unit for reproducing the traffic information on the basis of the received difference traffic information and the reference traffic information stored in the traffic information storage unit, wherein the difference traffic information is difference between the latest traffic information and the reference traffic information.
The traffic information distribution apparatus of the present invention includes predetermined identification information in the traffic information acquired or generated, accumulates the traffic information which includes the identification information in the traffic information accumulation unit and distributes the traffic information which includes the identification information to an in-vehicle terminal. The in-vehicle terminal receives the traffic information and holds the traffic information as reference traffic information. Then, the in-vehicle terminal transmits distribution request information including the identification information included in the reference traffic information to the traffic information distribution apparatus. The traffic information distribution apparatus receives the distribution request information, generates difference traffic information between the traffic information specified by the identification information included in the distribution request information and traffic information to be distributed, and distributes the traffic information to the in-vehicle terminal.
Other features and advantages of the present invention will become more apparent from the following detailed descriptions of the invention when taken in conjunction with the accompanying drawings.